Electroplating is a well-known process used in the microelectronics industry for depositing a metal film or forming other electrically conductive structures. For example, electroplating is commonly used for depositing a copper-based metallization layer from which interconnects in an integrated circuit (“IC”) can be formed. Other structures that can be formed using electroplating includes through-substrate interconnects, through-mask plated films, and electroplated bumps for flip-chip type electrical connections.
In many conventional electroplating processes, a substrate to be electroplated is held in a substrate holder and immersed in an electroplating aqueous solution. A consumable or inert anode is also immersed in the electroplating aqueous solution. The substrate holder can include a base and a cover having an opening formed therein that exposes a surface of the substrate when the base and cover are assembled together. The substrate holder can also include provisions for electrically contacting the substrate, such as electrical contact pins that contact a peripheral region of the substrate. The substrate functions as a cathode of an electrochemical cell in which the electroplating aqueous solution functions as an electrolyte. A voltage source may apply a voltage between the substrate and the anode to cause metal ions from the electroplating aqueous solution to deposit onto the exposed surface of the substrate and form a plated film.
It is desirable that the electrical contact pins reliably electrically contact the substrate within the substrate holder to ensure that the plated film is deposited on the exposed surface of the substrate under controlled electrochemical conditions. For example, moving the substrate holder carrying the substrate to immerse the substrate in the electroplating aqueous solution and aggressively moving the substrate holder carrying the substrate in the electroplating aqueous solution during the electroplating process can cause the electrical contact pins to lose or unreliably contact the substrate. If the electrical contact between the electrical contact pins and the substrate is not reliable, the quality and/or uniformity of the electroplated film may not be of acceptable quality for use in an IC.
In addition to the substrate holder providing a reliable electrical contact between the substrate and the voltage source, it is often desirable to seal the electrical contact pins and regions of the substrate that are not desired to be electroplated from the electroplating aqueous solution. When the electrical contact pins are not isolated from the electroplating aqueous solution, the electrical contact pins can also be electroplated and, consequently, cause variability in the electroplated film morphology and/or thickness.
Therefore, there is still a need for an improved substrate holder that is capable of isolating selected portions of a substrate from an electroplating aqueous solution and providing a reliable electrical contact to the substrate.